This invention relates to the chemical composition of a hot pack capable, when activated, of producing a safe and greatly extended exothermic reaction. The composition may be applied, for example, in a pack useful as a hand, foot or body warmer, a therapeutic device, or a device for heating foods and beverages. Its application, however, is not so limited, and such is not intended.
The composition of the invention is an improvement over that subject of U.S. Pat. No. 4,067,313, the most pertinent prior art of which the inventor and those substantively involved in the preparation of the present application are aware.
The composition of the referenced patent comprises a quantity of water and normally separated particulate material capable of producing an exothermic action when in contact with water. The particulate material of the patent consists essentially of, in parts by weight, about 40 to about 90 parts anhydrous calcium chloride, about 12 to about 25 parts anhydrous sodium acetate, and about 5 to about 15 parts calcium oxide. There is about 40 to about 90 parts by weight of the water which forms a moldable gel upon mixing thereof with the particulate material at ambient temperature. The mixture resulting is capable of producing and maintaining a temperature not in excess of about 107.degree. C. for a period of time up to about 20 minutes.
The invention subject of U.S. Pat. No. 4,067,313 did advance the art with which we are here concerned but its useful application has proven to be limited. Embodiments have been found to lack sufficient safety factors, a problem of serious concern when they are applied to use as therapeutic devices or to warm portions of the human body. Under certain conditions the compositions of the prior art will generate pockets of steam when embodied in a sealed container, the pressures of which are sufficient to rupture the container. The possible danger in this respect is believed obvious. More than this, while the prior invention was found to extend the effective life of hot packs, it has been also found that their life must be even further extended to achieve their general acceptance in a broad spectrum of industry.